Ticketmaster, the world’s largest seller of tickets, and Live Nation, the largest concert promoter, announced plans to merge last February. The deal requires approval from the Justice Department and from Canadian authorities.

Chip Somodevilla/Getty ImagesLive Nation President and CEO Michael Rapino, left, and Ticketmaster Entertainment CEO Irving Azoff are sworn in before testifying to a U.S. Senate committee in February.

The British commission originally ruled against the merger because it would prevent another company, CTS Eventim, from entering the British market. Since that October announcement, however, the commission said the partners provided evidence showing CTS Eventim would not be harmed.

U.S. Rep. Bill Pascrell (D-Dis.8), a harsh critic of the merger, expressed disappointment about the British decision. But he said the ruling asserts that the deal would squash competition in the United States, and therefore he hopes it might push federal regulators to deny the deal.

"The commission clearly states that the deal it sanctioned today allows Ticketmaster to remove a major competitor in the ticket services market in the United States, but that finding is not within the scope of their authority," said Pascrell. "While in the United Kingdom they only control about 50 percent of the market, the two companies combined control between 70 to 80 percent of the market here."

Pascrell testified before a Congressional panel in May and co-signed a letter with 50 lawmakers in July that outlined his opposition to the merger. Last week, a coalition of consumer and entertainment groups joined with him to launch a website, www.ticketdisaster.org, to continue to put pressure on the government to deny the merger application.